This invention relates to a method for preventing contrast associated nephropathy and to a catheter designed to be used in the process.
Percutaneous transluminal coronary angioplasty (PTCA) has advanced at a rapid pace in terms of efficacy and safety, and is currently the preferred approach in treating coronary atherosclerosis, which produces areas of blockage within a coronary artery.
Prior to performing PTCA and during the procedure itself an iodine containing dye or contrast material is injected into the patient""s artery through a catheter. The iodinated solution is fluorescent and enables the coronary arteries to be visualized. The use of the contrast solution, however, includes a certain amount of risk and even though non-ionic compounds, which are inert and hypoallergenic, have been developed, contrast associated nephropathy (damage to the kidneys) is a significant problem. It is common for patients to require revascularization of more than a single vessel but when there is danger of contrast induced renal failure, the vessels must be done on separate visits at greatly increased cost and inconvenience, in addition to the increased risk of arterial puncture. If it were possible to eliminate the risk of renal failure due to the contrast solution, multi-vessel interventions could be done at a single sitting.
In addition, there are many patients with chronic renal insufficiency who, after undergoing catheterization, must wait 24 to 48 hours in the hospital before undergoing PTCA in order to space the kidney load associated with the contrast load. Moreover, the elderly, particularly those with a pre-existing renal insufficiency, comprise a large group in which even angioplasty is not attempted because multi-vessel disease is anticipated and multi-vessel intervention may lead to the risk of renal failure.
Accordingly, despite the significant advances that have been made in treating the coronary arteries themselves (i.e. opening the stenosis with a stent and maintaining it open with anti-platelet drugs), the problems associated with contrast nephropathy have been a limiting factor on the extent to which these advanced angioplasty procedures can be used.
The principal object of the invention is to reduce, if not prevent, the incidence of contrast associated nephropathy during percutaneous coronary procedures.
It is a further object of the invention to provide a catheter which can be used to drain blood from the coronary sinus vein while preventing a substantial amount of the contrast solution from getting into the general circulation of the patient.
In accordance with the invention, when contrast solution is injected into the coronary artery of a patient, blood is prevented from flowing through the coronary sinus into the right atrium. Simultaneously, the blood in the coronary sinus is bypassed to a device which filters out the contrast solution from the blood and recirculates the blood back to the patient.
In a preferred embodiment, a balloon on a catheter is used to block blood flow from the coronary sinus to the right atrium. The catheter includes a port distal of the balloon so that when the sinus is occluded, blood flows from the sinus into the central lumen of the catheter where it can be directed to the filtration device. Preferably, the balloon is only inflated when the contrast solution is injected and the catheter includes supplemental means for retaining the catheter within the sinus when the balloon is deflated. The supplemental means may include an expandable mechanical device, a second inflatable balloon, or a deflectable tip which can be guided into a branch extending from the sinus.